A toxicity assessment of pulp mill biosolids to rainbow trout (Oncorhynchus mykiss)

The use of pulp mill solids wastes (biosolids) as a soil amendment on agricultural and silvicultural land is an increasingly common practice. To examine the fate of toxic wood extractives within biosolids, we sampled the final biosolids from thermomechanical (TMP) and bleached kraft (BKM) pulp mills using activated sludge treatment systems, and primary biosolids (TMP/BKM Primary) and secondary sediments (TMP/BKM Pond 3&4) from an aerated stabilization basin treatment system receiving the effluent from both TMP and BKM mills. Concentrations of wood extractives were determined using gas chromatography/mass spectrometry. Acute lethality and CYP1A induction were tested using a 96h juvenile rainbow trout assay, and chronic lethality and toxicity tested with a trout early life stage (ELS) assay. Findings suggest that wood extractives are not entirely mineralized in effluent treatment, and extractives associated with biosolids may continue to pose a hazard to aquatic species. (Abstract shortened by UMI.)...